Sound-proof wall made of FRP, and method of producing the same

ABSTRACT

A sound-proof wall made of FRP in the form of a sound-proof wall panel that includes a core and skin members made of FRP positioned on both sides of the core and whose weight per nit area is within the range of 10-60 kg/m 2 ; and a method of producing the same. This sound-proof wall, though light in weight, has a superior sound insulation property and will never corrode because it is made of FRP. Further, it has a high degree of freedom of engineering design including sound-proof property, design, and shape, capable of producing a desired sound-proof wall with case. Further, since it has a high specific strength, it is possible to attain a drastic weight reduction while retaining the necessary strength, and facilitate working, shorten construction time, and reduce construction cost.

TECHNICAL FIELD

This disclosure relates to a sound-proof wall made of a fiber reinforcedplastic (hereinafter, referred to as “FRP”) provided to railways, roads,etc., for the purpose of insulating noises generated by trains and cars,and a method for producing the same.

BACKGROUND

Noises induce complains and troubles most frequently among variouspollutions, and prevention of noise as a countermeasure against anenvironmental problem is an important social subject.

Generally, there are two kinds of members of a sound insulation memberand a sound absorbing member as sound-proof members for preventingnoise.

The sound insulation member functions to cut the propagation of soundenergy by reflecting a sound propagated in air, and the soundtransmission loss, which is an index of the sound insulation property,basically depends on mass low, and becomes greater as the mass becomesgreater. For example, mainly a concrete sound-proof panel or a metalsound-proof panel, such as those disclosed in, for example,JP-A-8-144227, is installed on a lowland portion or a high-level portionof a railway or a road for the purpose of reducing noise to inhabitantsin the regions along the railway or road, as known well.

Since such panels made of these materials are heavy, although they havecertain effects for preventing or diffusing noise generated from trainsor cars depending on mass low, in a case of a metal sound-proof panel,there is a problem in durability such as deterioration, and in a case ofa concrete sound-proof panel, recently there is a problem of flaking ofsmall concrete pieces due to bulging or cracking caused by causticembrittlement or rust of reinforcing steel. In particular, in a case ofsound-proof walls made of concrete blocks, damage to the walls such ascracks and gaps is severe, and in a case where the installation place isat a high level such as a high-level bridge of a railway, flakingthereof becomes a problem, and therefore, urgent exchange is consideredto be necessary.

Further, because the walls in both cases are great in specific gravityand heavy (for example, about 200 to 300 kg/m as a weight per unitlength in the horizontal direction in an installation place), it isnecessary to introduce heavy machines and an exclusive machine forattachment into an attachment place for conveying and attaching thewalls. Especially, in a case where the installation place is ahigh-level bridge of railway, there remain a problem that it isdifficult to approach the exclusive construction machine to theinstallation place of sound-proof walls from the railway line side, anda problem in workability because, even if the approach becomes possible,the work for installation inevitably becomes a high-level place workingfrom a position under the high-level bridge.

For such problems, sound-proof panels made of FRP containinglight-weight cores for the purpose of lightening are disclosed inJP-B-2-57691 and JP-A-9-170292. In these publications, because the useof sound-proof panels are limited mainly to outer walls of houses andbuildings, the sound-proof panels disclosed in these publications aredesigned for a case where a noise source is relatively far, and they arenot so high in sound insulation property. Further, small beams forattachment of the panels are provided in the lengthwise and crosswisedirections at a fine pitch, and they are constructed as those which donot require high mechanical properties such as strength and stiffness somuch.

However, in order to use the sound-proof panels as those for railways orroads, because noise sources are relatively close and the noise levelsare high, it is necessary to control their weights at proper weightsbased on mass low. At the same time, it is preferred to sustain a panelby itself without providing small beams at a fine pitch, and because awind pressure is applied, it is necessary to bear a wind pressure in therange of about 300 kg/m² to about 400 kg/m² per unit area. Namely, alight-weight sound-proof panel cannot be obtained unless an optimumdesign is performed with respect to sound insulation property andstrength while an attachment means to a construction body such as ahigh-level bridge, a bridge or an edge of a road is considered. Further,in a case where the installation place is a high-level bridge such as ahigh-level bridge of railway, the panel itself may become a great noisesource unless a resonance due to a vibration propagated from theconstruction body when a train is running is avoided.

Further, recently, for a sound-proof panel applied to a railway or aroad, sound-proof countermeasures for houses or educational institutionsadjacent to the railway or the road are further required, and the heightof the sound-proof panel tends to become higher in order to alsosuppress a diffracted sound. However, the present construction body orbeam has a weight limitation ascribed to the viewpoint of strength, andthe height of the panel cannot be increased to a height more than acertain level. Further, although a light sound-proof panel made ofacrylic is employed in consideration of such a weight limitation, thereare a problem of durability due to a strength reduction ascribed to adeterioration by ultraviolet ray in a relatively short period, and aproblem that the construction cost is not always cheep as a whole,because the strength and the stiffness are small and it is necessary toprovide support poles and cross beams at a small interval though thesound-proof panel itself is light.

On the other hand, since the aforementioned sound absorbing memberfunctions to damp a sound pressure by transforming a sound energy into athermal energy, the sound absorbing member by itself is low in soundinsulation property, and therefore, it is a general use to use ittogether with a sound insulation member, thereby increasing the soundinsulation property. The invention using such a sound absorbing memberand increasing the sound insulation property is disclosed in, forexample, JP-A-2000-8331.

That invention disclosed is a sound-proof panel having a structure inwhich the sound insulation portion comprises a concrete sound insulationwall, therebehind an FRP sound absorbing plates are disposed at apredetermined interval, and an air layer is provided therebetween.Although this panel appears to be excellent in sound insulationproperty, because the sound insulation panel itself is made of concrete,there is still a problem of the aforementioned partial flaking ordropping of small pieces due to caustic embrittlement or temporaldeterioration. Although it is tried to cover concrete with glass fiberreinforced plastic and prevent the flaking, it has not yet reached anessential improvement. Further, in a case of new installation, becausethe panels are made of concrete, heavy machines are required similarlyto in the cases aforementioned.

It could therefore be advantageous to provide a sound-proof wall panelmade of FRP and a sound-proof wall using this panel which have an effectfor preventing a noise or diffusing or absorbing the noise, and do notcause flaking of small pieces due to deterioration thereof as in theconventional sound-proof walls made of concrete, which are light andexcellent in handling property, and which can be installed easily evenif the installation place is a high-level place, and a method forproducing the same.

SUMMARY

We provide a sound-proof wall panel made of FRP comprising a core andskin members made of FRP positioned on both sides of the core, and itsweight per unit area is within the range of 10-60 kg/m².

There are two kinds of members of a sound insulation member and a soundabsorbing member as sound-proof materials of the panel for preventingnoise, for example, when the above-described panel is formed as athree-layer structure of an FRP sound insulation panel portion, a soundabsorbing body and an FRP perforated panel portion, because the energyof a sound entering from the perforated panel portion is damped by thesound absorbing body and the energy is further damped by the soundinsulation panel portion, more preferable sound-proof effect can beobtained.

A sound-proof wall made of FRP comprises a support pole providedintegrally with the above-described panel, and the support pole supportsthe panel and ahs an attachment portion attached to a construction at alower position.

Further, a method for producing a sound-proof wall made of FRP comprisesa method for producing a sound-proof wall panel by any of the followingmolding methods. Namely, a method for producing a sound-proof wall madeof FRP comprises the steps for molding a sound-proof wall panel ofplacing reinforcing fibers for a skin member, which forms a surface of amolded product, in a mold, placing a core, which has a resin channel fordistributing an injected resin, on the reinforcing fibers, thereafterplacing reinforcing fibers for a skin member, which forms a back surfaceof the molded product, on the core, and while reducing a pressure in themold, injecting a matrix resin into the resin channel impregnating andcuring the resin. Alternatively, a method for producing a sound-proofwall made of FRP comprises the steps for molding a sound-proof wallpanel of placing reinforcing fibers for a skin member, which forms asurface of a molded product, in a mold at a state in which a matrixresin is impregnated into the reinforcing fibers, placing a core,thereafter placing reinforcing fibers for a skin member, which forms aback surface of the molded product, on the core at a state in which amatrix resin is impregnated into the reinforcing fibers, and whilereducing a pressure in the mold, curing the matrix resin. Alternatively,a method for producing a sound-proof wall made of FRP comprises thesteps for molding a sound-proof wall panel of, after molding a skinmember forming a surface of a molded product and a skin member forming aback surface of the molded product separately, forming a hollowstructural body by bonding both skin member, and charging a corematerial into a hollow portion of the hollow structural body.Alternatively, a method for producing a sound-proof wall made of FRPcomprises the steps for molding a sound-proof wall panel of forming ahollow structural body by molding a sound-proof wall panel of forming ahollow structural body by molding a skin member forming a surface of amolded product and a skin member forming a back surface of the moldedproduct substantially simultaneously, and charging a core material intoa hollow portion of the hollow structural body.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a partially cut-away perspective view of an FRP sound-proofwall.

FIG. 2 is a partially cut-away perspective view of another FRPsound-proof wall.

FIG. 3 is a partially cut-away perspective view of still another FRPsound-proof wall.

FIG. 4 is a partially cut-away perspective view of a further FRPsound-proof wall.

FIG. 5 is a sectional view of yet another FRP sound-proof wall.

FIG. 6 is a perspective view of still a further FRP sound-proof wall.

FIG. 8 is a perspective view of an FRP sound-proof wall and itsattachment structure portion.

FIG. 9 is a schematic sectional view of an FRP sound-proof wall.

FIG. 10 is a schematic sectional view of another FRP sound-proof wall.

FIG. 11 is a schematic sectional view of yet another FRP sound-proofwall.

FIG. 12 is a partially cut-away perspective view of an FRP sound-proofwall.

FIG. 13 is an enlarged partial sectional view of the FRP sound-proofwall shown in FIG. 12.

FIG. 14 is a perspective view of an FRP sound-proof wall

FIG. 15 is a perspective view of another FRP sound-proof wall.

FIG. 16 is a perspective view of a further FRP sound-proof wall.

FIG. 17 is a perspective view of FRP sound-proof walls and theirattachment structure portions, showing an embodiment of a plurality ofFRP sound-proof walls connected to each other.

FIG. 18 is a perspective view of an FRP sound-proof wall.

FIG. 19 is a view showing structures of respective samples in Example 4and Comparative Example 3.

FIG. 20 is a graph showing relationships between frequency bands andtransmission losses of respective samples in Example 4 and ComparativeExample 3.

FIG. 21 is a graph showing relationships between thickness ratios andproof stress ratios of respective samples in Example 4 and ComparativeExample 3.

FIG. 22 is a graph showing relationships between thickness ratios andunit weights of respective samples in Example 4 and Comparative Example3.

FIG. 23 is a graph showing relationships between thickness ratios anddeformation degrees of respective samples in Example 4 and ComparativeExample 3.

FIG. 24 is a graph showing relationships between thickness ratios andflexural stiffnesses of respective samples in Example 4 and ComparativeExample 3.

EXPLANATION OF LABELS

-   1, 1 a, 1 b, 1 c, 11, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121,    131: sound insulation panel-   2, 2 a, 2 b, 12, 22, 32, 82, 92, 132: skin member-   3, 13, 23, 33, 83, 93, 103, 133: core-   4, 24, 103, 139: reinforcing rib-   25: hollow portion-   34: stiffener-   42: support pole-   52, 84, 112, 124, 138: pole body-   52 a, 72, 137: attachment portion-   63, 73, 125: chemical anchor-   64, 74: metal plate-   65, 75, 126: nut-   62, 76, 123: construction body-   66: cover-   85: rough surface-   86: layer provided for the purpose of forming a rough surface-   87: layer provided for the purpose of obtaining strength or    stiffness-   88: colored layer-   94, 104: sound absorbing body-   95, 105: perforated panel-   96, 106: opening portion-   102: FRP single plate-   113: folded portion-   122: overlapping portion-   134: light transmitting material-   135: sound insulation body-   136: metal frame

DETAILED DESCRIPTION

Hereinafter, desirable embodiments of a sound-proof wall made of fRP anda method for producing the same will be explained referring to thefigures.

As aforementioned, there are two kinds of members of a sound insulationmember and a sound absorbing member as sound-proof members forpreventing noise. A sound-proof wall, which is a first structure, isformed in a structure having a skin member made of FRP in which a soundinsulation panel aims only a sound insulation effect, and a core.Further, a second structure of a sound-proof wall is formed in astructure having three layers of the above-described sound insulationpanel, a sound absorbing material having a sound absorbing function, andan FRP perforated panel preventing dispersion of the sound absorbingmaterial.

For the sound-proof wall panel, in a case of a relatively low noiselevel where a desired sound-proof effect can be obtained only by soundinsulation, the sound insulation panel may be used solely.

As the matrix resin of FRP portion forming the skin member, for example,a thermoplastic resin such as polyethylene, polypropylene, nylon, ABS,PEEK or polyimide, or a thermosetting resin such as epoxy resin,unsaturated polyester resin, vinylester resin or phenolic resin, can beused.

To these resins, a damping agent such as a stratified compound (forexample, mica, molybdenum disulfide, boron nitride, etc.), an acicularcompound (for example, xonotlite, potassium titanate, carbon fiber,etc.) or a particulate or plate-like compound (for example, ferrite,talc, clay, etc.) can be added. By adding a damping agent,transformation into frictional heat due to mutual movement betweencrystals of inorganic substances or between an inorganic substance and amatrix resin is performed, the elastic modulus and the density areincreased by charging the above-described filler, the kinetic energy ofvibrating materials is extinguished, and the vibration of the panel canbe reduced.

Further, a flame retardant (for example, aluminum hydroxide, bromine,inorganic powder, etc.) can be added to the above-described matrix resinto increase the flame resistance. Further, because a phenolic resin as amatrix resin is excellent in flame resistance by itself and it isinexpensive, it is preferably used. The above-described additives may beappropriately selected depending on places to be installed, namely,depending on a place requiring to prevent spreading fire, a placeremarkable in propagation of vibration, etc.

As reinforcing fibers for FRB, inorganic fibers such as glass fibers orcarbon fibers, or organic fibers such as aramide fibers, nylon fibers orpolyester fibers can be used appropriately depending upon the use andthe conditions for usage Further, as the formation of the used fibers,for example, a mat comprising short fibers preferably with a fiberlength of 1 to 3 mm, a cloth or strand comprising continuous fibers, andthe like, can be preferably used.

Although carbon fibers are most preferable as the reinforcing fibers inorder to obtain a light-weight and high-strength FRP, hybrid reinforcingfibers of glass fibers and carbon fibers are also preferably used, andthe volume ratio is preferably in a range of 1:0.05 to 1:1. Further,there is an advantage for increasing vibration damping property bycontaining carbon fibers.

Although the kind of used carbon fibers is not particularly restrictedfrom the viewpoint of strength and stiffness, in consideration of lowercost, it is most preferable to use so-called large-tow carbon fibers.For example, it is not to use a usual yarn whose number of filaments perone carbon fiber yarn is less than 10,000, but it is preferable to use atow-like carbon fiber filamentary yarn whose number of filaments per oneyarn is, if possible, in a range of 10,000 to 300,000, more preferablyin a range of 50,000 to 150,000, because such a yarn is more excellentin impregnation property of resin, handling property as a reinforcingfiber substrate, and economic condition for a reinforcing fibersubstrate.

The above-described mat is obtained by cutting filamentary yarns ofglass fibers, carbon fibers, etc. at a length of about 1 mm to about 3mm and making a sheet form using a binder such as polyvinyl alcohol(PVA), and a flat surface can be obtained by disposing it on a moldedproduct. Further, a cloth substrate comprising warps and wefts isobtained by weaving the above-described filamentary yarns by a weavingmachine. The mat substrate may be disposed in order to increase aboundary delamination resistance between layers of a cloth substrate ora unidirectional substrate comprising laminated continuous fibers.

Further, an FRP skin member can be form by various molding methods suchas a first-group molding method selected from the group of vacuum, blow,injection, stamping, BMC (bulk molding compound), SMC (sheet moldingcompound) and transfer molding methods, and a second-group moldingmethod selected from the group of RTM (resin transfer molding), press,pultrusion and hand-lay-up molding methods.

The above-described first-group molding method is a method frequentlyused in a case of combination of a short fiber substrate and athermoplastic resin or a thermosetting resin. Although this moldingmethod has a weak point of slightly low strength and stiffness becausethe used reinforcing fibers are short fibers, it is frequently usedbecause the molding cycle is short, the manufacturing cost is low, andribs, etc. for giving an excellent function as a structural body can beeasily molded, and strength and stiffness much higher than those of abody made of a plastic only can be obtained by this method. Theabove-described second-group molding method is a method frequently usedin a case of combination of a long fiber substrate and a thermosettingresin, and it is possible to form ribs similarly to in theabove-described method. In particular, by a vacuum injection andimpregnation molding which is a simple RTM, the volume content ofreinforcing fibers, etc. can be increased, and there is an advantagethat a product having high strength and stiffness can be manufacturedrelatively inexpensively.

In the above-described substrate, as needed, or in accordance withrequired mechanical properties, etc., a plurality of reinforcing fiberlayers are stacked to form a reinforcing fiber substrate, and a resin isimpregnated into the reinforcing fiber substrate. A unidirectional fiberlayer or a woven fabric layer can be appropriately employed as thereinforcing fiber layer to be stacked, and it is preferred toappropriately select the direction of the fiber orientation thereofdepending upon a required strengthening direction. The volume content ofreinforcing fibers Vf in this case is preferably in a range of 15 to60%, more preferably in a range of 30 to 50%, from the reason to ensurestrength and stiffness necessary for an FRP structural body (in thiscase, a sound-proof panel).

As described above, it could be advantageous to obtain a sound-proofwall light in weight and good in handling without requiring a heavymachine at the time of construction and easy in construction wileensuring necessary mechanical properties (strength and stiffness), andanother purpose is to give an excellent sound insulation property.

From such a point of view, generally, the sound insulation property of asound insulation material is indicated by a sound transmission loss (TL)defined by an equation of TL=10 log₁₀(1/τ) expressed by decibel (dB) asits unit. The transmission rate (τ) is expressed as a ratio of atransmitted energy (It) relative to an incident sound energy (Ii) to thesurface of a material and defined as an equation of τ=(It/Ii), and onlya sound transmitted through the material becomes its object. Althoughusually the transmission loss of a sound insulation material isbasically depending on mass law and the greater the mass is, the greaterthe loss becomes, a transmission loss of 10 dB or more in an audiblerange of 125 Hz to 4 kHz is required for a sound insulation panel usedin a railway or road. Namely, it must be a material capable ofinsulating 90% or more of a sound energy. In order to achieve this in anFRP sound-proof wall, it is necessary to set the weight of a soundinsulation portion at 10 kg/m² or more, and if the weight is less thanthis value, a necessary transmission loss cannot be obtained. Althoughit is possible to use only an FRP single plate having a thickness of 6mm or more if only the transmission loss is considered, in order toresist against a wind pressure of 300 kg/m² to 400 kg/m² per unit areawhile to support itself as a sound-proof wall, it is necessary that theflexural stiffness per unit width is 0.1×10⁷ kg·mm or more, and it isnecessary to increase the thickness of the FRP. However, the method forsimply thickening the FRP is not a preferred design from the viewpointof cost and lightening, and it is preferred to form a sandwichstructural body or a structural body having a stiffener on the backsurface as a basic structure of a sound-proof wall. By this, it becomespossible to obtain a light sound-proof wall panel while ensuring anecessary stiffness. In order to obtain such lightness and necessarymechanical properties, the ratio of the total thickness of a panel T toa thickness of each FRP skin member t1 is preferably within the range of5:1 to 50:1.

Next, preferred examples of the above-described FRP sound-proof wallpanel and tRP sound-proof wall will be explained in more detailreferring to the drawings.

FIG. 1 is a partially cut-away perspective view of an FRP sound-proofwall. In FIG. 1, a sound insulation panel (1) is constructed from a core(3) and skin members made of fRP (2) positioned on both sides of thecore (3).

In this structure, skin members (2) are made of an FRP which containsreinforcing fibers at a volume content Vf of 15 to 60%, and they areinevitable members in order to ensure strength and stiffness formaintaining a shape as a panel structural body and for resistanceagainst a required load (for example, a wind pressure, a collision of asmall flew material, etc.). Preferably, if the volume content Vf iswithin a range of 30 to 50%, it is possible to prevent deterioration ofthe matrix resin more properly while keeping the necessary mechanicalproperties (strength and stiffness). Further, it is preferred that alayer comprising a CFRP (carbon fiber reinforced plastic) is containedat 5% or more in thickness ratio at least relative to the skin members(2). Preferably, it is in the range of 5 to 20%. An appropriate designof the kind and amount of the reinforcing fibers and the kind of thematrix resin provides an advantage to increase the flexural stiffnessper unit width of the panel as well as to increase the natural frequencyof the panel.

Various materials can be used as the material of core (3), and materialssuch a inorganic and organic materials, dried sludge, burned ash, etc.can be used. For example, As the inorganic materials, there are metalpowder such as aluminum or copper, a siliceous material such as aquartzite or a diatom earth, an aluminate material such as an alumina, amica or a clay, a calcareous material such as calcium carbonate or agypsum, a carbide such as graphite or carbon black, concrete (cement),mortar, etc. In particular, it is preferred to mix ferrite particles inconcrete (cement) because a function as a wave absorber panel is added.Further, as the organic materials, there are a linter, a linen, a wood(powder) or sea weed powder which is vegetative or animal, and asynthetic resin such as polyamide, viscose, acetate, etc. Further,although a part of dried sludge or burned ash is recycled by burying itor utilizing it as a charging a meterial for a brick and the like,because the handling is troublesome, most of them are conveyed to adisposition place and served to a declamation. Although the treatment ofthem is expensive, they are extremely inexpensive as a raw material. Adamping material may be used for core (3), and as such a dampingmaterial, there are a viscoelastic material (for example, butyl rubber,neoprene rubber, urethane rubber, etc.) or a resin or liquid containingpowder thereof, a soft vinyl chloride resin, EVA, asphalt, etc. Ofcourse, a resin added with the aforementioned stratified compound,acicular compound, or particulate or plate-like compound, etc. can beused as a charging agent. The panel having this structure is good invibration damping property, and it is suitable particularly for a placeviolently vibrated.

Further, as the formation of core (3), there are a solid or powder whoseraw material is the above-described inorganic material or organicmaterial, a foamed material whose raw material is an urethane, styrene,or phenol resin and the like, and an aqueous solution or gel liquid ofwater, polyvinyl alcohol, ethylene glycol, silicone, etc., and amaterial prepared by solidifying a powder material with a resin may beemployed. Although the formation of core (3) is not particularlyrestricted, it is preferred to use a foamed material having a smallspecific gravity, a resin blended with shirasu balloons or glassballoons, a balsa wood, etc., because a light sound insulation panel canbe obtained. In any case, it is preferred to select the materialappropriately in consideration of the cost, weight, property andhandling property of the panel. Of course, a combination thereof may beemployed.

The sound insulation panel (1) may have a sandwich structure as shown inFIG. 1 or a stiffener structure as shown in FIG. 15 described laterwherein an FRP reinforcing material is substantially integrated on onesurface or both surfaces of an FRP single plate in its lengthwise andcrosswise directions or either direction. Although the formation is notlimited to these formations, the flexural stiffness per unit width ofpanel is preferably in a range of (0.1 to 10)×10⁷ kg·mm. The reason is,for example, in that such a stiffness is necessary in order to ensure astrength and a stiffness against a load such as a wind pressure when thesound insulation is disposed between support poles set at apredetermined interval. Namely, if the flexural stiffness is less thanthis range, the vibration becomes great by fluttering, not only thepanel may become a vibration generation source but also the panel islikely to generate a resonance, and it becomes difficult also to ensurethe necessary strength. On the other hand, if flexural stiffness is morethan this range, the unit weight of the panel increases, it may becomenecessary to sue a heavy machine at the time of construction, and thehandling property thereof maybe damaged.

The reason why the ratio of the total thickness of the panel T to athickness of each skin member t1 is within the range of 5:1 to 50:1, isin that, if the thickness t1 of skin member (2 a, 2 b) is greater thanthis range, the lightness may be damaged, and on the contrary, ifsmaller than this range, the strength may not be exhibited sufficiently.Namely, when the compression strength and the shear stiffness are greatsuch as a case where the above-mentioned core (3) is made of a solidmaterial, a low-degree foamed material, etc., even if the thickness ismall, the panel can resist as a structural body against theabove-described load, but in a case where the core (3) is made of powderor liquid, namely, in a case where enough compression strength and shearstiffness cannot be expected, it is necessary to realize a structuralbody capable of resisting the above-described load only by the FRPportion. Therefore, it is preferred to design the thickness of the skinmember depending on the required mechanical properties such as strengthand stiffness.

Further, the total thickness of the panel has a relationship with asound insulation property which is in close relation with mass law, andwhen the density of the whole panel is small, the panel requires a largethickness, and when the specific gravity of a core is great, because thepanel itself becomes heavy, the panel may be formed at a small thicknessas a whole. In any case, it is preferred to design the panel inconsideration of frequency band of noise, level of transmission loss andcost.

Furthermore, in order to obtain a sound-proof wall panel which canimprove the mechanical properties such as strength and stiffness, thelightness and the sound insulation property more than those of theabove-described panel, it has been found that the weight per unit areaof panel is necessary to be within a range of 10 to 60 kg/m². Thisweight can be adjusted by appropriately selecting the thickness of theskin member and the kind and density of the core. If the weight per unitarea is smaller than 10 kg/m² the above-described sound insulationproperty due to mass law is remarkably damaged, and if the weight isgreater than 60 kg/m², although the sound insulation effect can beimproved, it becomes heavy and the handling property deteriorates.

FIGS. 2 and 3 show sound insulation panels (11, 21) different from thatshown in FIG. 1. FIG. 2 shows a structure wherein reinforcing ribs (14)are provided on the inner walls of FRP skin members (12) forming a soundinsulation panel (11), and core (13) is disposed inside of the panel.Since the strength and stiffness of a sound insulation panel areflexural properties of a structural body, they are greatly influencednot only by the tensile/compression properties of skin members (12) butalso by shear property of core (13). Therefore, in a case where amaterial attaching importance to lightness is selected as the materialof core (13), the strength and stiffness may decrease. In order toprevent this, it is preferred to provide FRP reinforcing ribs (14) incore (13) of sound insulation panel (11). FIG. 3 shows a structurewherein reinforcing rib (24) is provided so as t connect FRP skin member(230 confronting each other and forming sound insulation panel (21), andthe panel ahs core (23) therein. In the structure shown in FIG. 3, apart of portions surrounded by reinforcing rib (24) may be a hollowportion (25) in order to further lighten the panel.

In such a structure, the interval of reinforcing ribs (14) provided inthe vertical and horizontal directions or one of the directions ispreferably within a range of 10-500 mm. The reason is in that, if withinthis range, small beams are not necessary between the support poles andnecessary strength and stiffness can be ensured only by the panel.Where, reinforcing ribs (14, 24) can be extended in both the verticaland horizontal directions or one of the directions. The position and thenumber of the ribs may be appropriately considered depending upon thestrength and stiffness required in accordance with the load applied to aportion between support poles and the panel. The interval of reinforcingribs (14, 24) is preferably within a range of 25 to 450 mm. If withinthis range, the thickness of skin members (12, 22) can be smallened,they can be further lightened, and a necessary plane stiffness can beensured. Where, in a case where core (13, 23) is made of liquid materialor powder material, such a structure having reinforcing ribs (14, 24) ispreferred, but in a case where the core is made of a materialsolidifying powder material with a resin, a foamed material, a wood,cement or mortar, because the material itself has a necessarycompression strength and shear stiffness required for a core, thereinforcing ribs are not always required, and therefore, it is preferredto design the structure depending on the formation of the core (13, 23).By providing reinforcing ribs (14, 24), the strength and stiffness ofsound insulation panel (11, 21) are not influenced by the shear propertyof core (13, 23), and as a result, there is an advantage capable offreely selecting the material of the core (13, 23) as aforementioned.

FIG. 4 shows an FRP sound-proof wall and shows a ease where soundinsulation panel (31) has stiffeners outside of it. FIG. 4 shows anexample of a structure in which a substantially integrated stiffeners(34) are provided outside of sound insulation panel (31) formed by FRPskin member (32) and core (33). In this structure, stiffeners (34)exhibit an effect similar to that by the aforementioned reinforcingribs, the stiffness as whole panel can be increased, the thickness ofthe whole panel can be decreased, and therefore, the panel can befurther lightened.

FIGS. 5, 6, 7 and 8 show examples of an attachment portion and anattachment structure of an FRP sound-proof wall. FIG. 5 shows astructure in which panels are connected to each other and integratedwith each other via a support pole disposed therebetween, and showsstructure wherein FRP sound insulation panels (41) are fitted into orinserted into support pole (42) made of a material of metal, an FRP,etc. According to this method, there is an advantage that the panels canbe disposed in a limited space and a complicated attachment structure isnot required. Further, since the portions of support pole (42) disposedon both surfaces of sound insulation panels (41) are connected to eachother to be integrated, the support pole (42) can efficiently fix andsupport the sound insulation panels (41) even if the support pole (42)is small-sized.

FIGS. 6 and 7 show FRP sound-proof walls. In the structure shown in FIG.6, poles (52) are provided integrally with sound insulation panel (51)which is formed in a sandwich structure comprising a core and FRP skinmembers positioned on both surfaces of the core similarly to that sownin FIG. 1. Poles (52) extend down to a position below sound insulationpanel (51), and these extending portions are formed as attachmentportions (52 a) to be attached to a construction body. FIG. 7 shows andexample of an attachment structure wherein FRP sound-proof wall (61)having a structure similar to that shown in FIG. 6 is attached toconstruction body (62) such as a high-level bridge, and for example, thewall (61) is fixed to the construction body (62) via chemical anchors(63), a metal plate (64) functioning also as a support pole, and nuts(65). Further, in the structure shown in FIG. 7, the attachment portionis covered with a cover (66). Partially flaking of a concreteconstruction and dropping of small concrete pieces may occur not only ona portion of a sound-proof wall but also on a construction body itselfIt is not easy to exchange the construction body differently from thesound-proof wall. However, because such flaking and dropping do notinfluence the strength and durability of the construction body itself,only dropping to a ground may be prevented. In the structure shown inFIG. 7, in order to prevent small concrete pieces flaked fromconstruction body (62) from being dropped to a ground, cover (66) isformed to be able to be attached/detached and to be easily inspected asto whether flaking of concrete occurs, and as needed, repairing may beeasily carried out. Although the material of the cover is notparticularly limited, it is preferably made of the same FRP as that ofthe sound-proof wall, and by this, can be realized a cover light andeasy in attachment/detachment and excellent in surface design.

Where, as shown in FIG. 7, it is possible to make pole body (64) from ametal, and the advantage by making the pole body (64) from a metal is inthat, since the metal body is generally great in strength as comparedwith an FRP body even if the shape is same, as shown in the figure, ashape design good in space efficiency, which has no projection such asan attachment portion on the back of the sound-proof wall, can be easilycarried out. However, because the strength per unit weight is generallysmaller than that in an FRP body, the weight increases. Therefore, asshown in FIG. 6, FRP pole (52) may be employed.

FIG. 8 shows an FRP sound-proof wall A structure is employed whereinattachment portions (72) are provided on a lower portion of soundinsulation panel (71) and substantially integrated therewith. Eachattachment portion (72) is formed in a triangle shape, and fixed toconstruction body (76), for example, via chemical anchors (73), a metalplate (74) and nuts (75). However, since it may be fixed to aconstruction body having a concrete surface, a metal surface, etc. viaappropriate fasteners such as bolts and nuts, the fixing means, shape,material, dimension, etc. thereof are not limited. This structure issuitable for application to, for example, a case where there is arestriction in construction and it is impossible to project parts to anouter side, such as a case of a high-level bridge. Further, as themethod for attaching a sound-proof wall panel to a construction body,except the attachment method in the above-described structure byfasteners, for example, a method for bonding an attachment portion to aconstruction body using a resin-system adhesive, or a method for buryingan attachment portion into a construction body by placing of mortar, canalso be employed. The method is not always limited to this embodiment,and it is preferred to appropriately select the attachment methoddepending upon circumstances and place for the attachment.

FIGS. 9, 10 and 11 show that the sectional shape of a sound insulationpanel in the FRP sound-proof wall can employ various shapes except theflat-plate shape shown in FIG. 1, and these shown sectional shapes canbe applied for any of the cross-sectional shape and the verticalsectional shape of a panel. FIG. 9 shows a sound insulation panel (1 a)having a wave-type sectional shape, FIG. 10 shows a sound insulationpanel (1 b) having a hat-type sectional shape, and FIG. 11 shows a soundinsulation panel (1 c) having an arc-type sectional shape. The sectionalshape of the panel may be another shape, and it is not particularlylimited. It is preferred to select the shape in consideration ofstiffness, appearance, design, etc. as a structural body.

FIG. 12 shows an example wherein the surface of a sound insulation panel(81) is formed as a rough surface having a random irregularity, and FIG.13 is an enlarged view of the rough surface portion.

The sound-proof wall in the figures comprises a sound insulation panel(81) constructed from a core (83) and FRP skin members (82) positionedon both surfaces of the core (83), and support poles (84) formingattachment portions thereof, and the surface of at least outer-side skinmember (82) of the sound insulation panel (81) or a layer added to theouter side of the outer-side skin member (82) is formed as a roughsurface (85). Rough surface (85) is formed as a convex/concave surfacein which convex portions and concave portions are randomly disposed, andthe mean value of the difference between the heights of the convexportions and concave portions is not less than 0.5 mm. Further, the FRPskin member forming rough surface (85), for example as shown in FIG. 13,is formed as a structure which has two layers of a layer (86) for thepurpose of at least forming the rough surface (85) and a layer (87) forthe purpose of obtaining a strength and a stiffness, and on the outerside of the layer (86) (as an outermost layer), further has a coloredlayer (88) which is provided for the purpose of improving the appearance(design) and which also has a function of preventing deterioration ofresin due to ultraviolet rays. By such a separation into the respectivelayers, it becomes possible to prevent the orientation of reinforcingfibers for obtaining a strength and a stiffness from being locally bentby the influence due to the irregularity of the surface and to preventreduction of strength. Further, because the layer (86) does not requirea strength, it may be formed, for example, by a layer containing a matof reinforcing fibers, which can easily form the rough surface (85). Thelayer (87) is the same layer as that of the aforementioned skin member(2), and it is formed by a reinforcing fiber substrate such as aunidirectional substrate or a woven fabric substrate in order to obtaina strength and a stiffness. The colored layer (88) is formed from, forexample, a gel coated layer having two or more colors or a resincontaining a pigment.

In order to form the convex/concave surface, although either a methodfor placing an elastic material such as a rubber in a mold andtransferring the pattern of the material or a method for using a moldpreformed with a convex/concave pattern on the molding surface of themold may be employed, the method using an elastic material has anadvantage capable of forming convex/concave surfaces with variouspatterns only by changing the elastic material. Further, by formingrough surface (85) on the outer surface, even if the surface is exposedto the direct rays of the sun, it is possible to prevent a dazzlingfeeling from being given to a passer-by or a resident nearby byreflecting the rays. Further, by coating the surface with the coloredlayer, not only the design of the appearance can be improved but alsothe deterioration of the FRP portion due to ultraviolet rays can beminimized, and therefore, the panel becomes to be suitable for useoutside.

FIG. 14 shows an FRP sound-proof wall and FIG. 15 shows an FRPsound-proof wall according to an structure different from the structureshown in FIG. 14.

In the structure shown in FIG. 14, sound insulation panel (91) is formedas a sandwich structure comprising a core (93) and FRP skin members (92)disposed on both surfaces of the core, and formed in a structure whereina sound absorbing body (94) is provided on both surfaces or one surfaceof the sound insulation panel (91) and a perforated panel (95) coveringthe sound absorbing body (94) is provided. In the structure shown inFIG. 15, sound insulation panel (101) is formed as a stiffener structurein which an FRP reinforcing member (103) is substantially integratedwith an FRP single plate (102) on one surface of the FRP single plate(102) in the lengthwise and crosswise directions or either direction,and formed in a structure wherein a sound absorbing body (104) isprovided on both surfaces or one surface of the sound insulation panel(101) and a perforated panel (105) covering the sound absorbing body(104) is provided. As aforementioned, the sound transmission loss, whichis an index of the sound insulation property, basically depends on masslaw, and the greater the mass is, the greater the loss becomes. However,in a case where a better sound insulation property as a sound insulationpanel is required such as a case where there is only a small space forinstallation, housing is closer, or there is a restriction in weight asa sound-proof wall, there is a limit in sound-proof property in astructure in which the sound-proof wall is formed only from theabove-mentioned sound insulation panel structural body. Accordingly, byusing together a sound-proof wall comprising a sound insulation paneland a sound absorbing body, it becomes possible that a sound havingentered from the direction of the perforated panel is absorbed, thelevel of the sound pressure is decreased, the sound energy is furtherdecreased by a vibration system based on the mass law in the portion ofthe sound insulation panel provided as an outer layer, and thesound-proof effect can be increased.

The sound absorbing property of a sound absorbing material used in theabove-described sound absorbing body changes generally depending on theincident angle of the sound, and the sound absorbing rate (α) of thesound absorbing material is defined as a ratio (α=(It+Ia)/Ii) of the sumof a transmission energy (It) and an energy (Ia) absorbed in theinterior of the material relative to an energy (Ii) of an incident soundto the surface of the material. The sound absorbing material isclassified by its structure (thickness, porosity, etc.) and appearance,and the material comprises a porous material (a rock wool or an asbestoscomprising cotton-like mineral fibers, a glass wool comprising glassfibers, a felt material punching these materials, a sponge comprising asoft urethane foam, etc.), a plate-like material (a plywood, an asbestoscement, a gypsum board, etc.), or a perforated material thereof, and theporous material has become a main material used as a sound absorbingmaterial because it is a material having a great sound absorbing rateover a broad frequency range. In this connection, when a glass wool isexemplified and the change of its sound absorbing rate is determined,the sound absorbing rate is in a range of 50 to 70% at a thickness of 13mm in the audible frequency range of 125 Hz to 4 kHz, and the soundabsorbing rate is in a range of 30 to 90% at a thickness of 75 mm. Thesound absorbing rate of a plate-like material is about 50% irrelativelyto its thickness. Namely, the sound absorbing body aims to reduce thesound reflected from the material, the above-described porous materialis suitable therefor such as a wool-like material, a foam, a felt, anonwoven fabric, etc., and such a material can exhibit a great soundabsorbing effect in a broad frequency range. Except such a material,perforated gypsum board, etc. may be employed, further, a combination ofthese materials may be employed, and it is preferred to appropriatelyselect the material depending on the frequency to be absorbed. Apreferable thickness is in a range of 11 to 80 mm.

Further, as aforementioned, the sound absorbing material functions todamp a sound pressure, the material solely is low in property forinsulating a sound, and by using it together with a sound insulatingmember, the sound insulation property can be improved, and therefore,usually it is used at a condition being bonded to a back surface of aninorganic board or a concrete wall. Therefore, as FRP sound insulationpanel (91, 101), it is preferred that perforated panel (95, 105), soundabsorbing body (94, 104) and sound insulation panel (91, 101) aredisposed in this order as viewed from the side of a noise source. In acase where there are noise sources on both sides, the preferabledisposition, of course, should be in an order of a perforated panel, asound absorbing body, a sound insulation panel, a sound absorbing bodyand a perforated panel.

Where, the FRP perforated panel functions to prevent scattering of thesound absorbing material of the sound absorbing body comprising theporous material described below, and the thickness thereof may be in arange of 1 to 3 mm. The perforated panel is a kind of a cover fordamping the incident sound energy at the sound absorbing body withoutreflecting the sound at the surface of the material by existence ofopening portions (96, 106) as shown in FIGS. 14 and 15, and therefore,although a certain degree of strength is required therefor, the openingrate may be in a range of 50 to 90%. Where, the opening rate of aperforated panel is defined as a rate determined by dividing an area ofan opening or of a portion cut away in a form of a rectangle with anarea without an opening or without a cut-away portion. However, theperforated panel is not always necessary in a case where the soundabsorbing body comprises a felt or plate-like material formed at a highdensity and the sound absorbing body itself can maintain the self shapeor has a certain-level high strength.

Although the perforated panel is shown as a lattice-type structural bodyin FIGS. 14 and 15, a plate having holes may be employed, and the shapeand structure may be arbitrarily designed, it is not particularlylimited. However, if the opening rate is too small, the reflection ofsound increases, and if the opening rate is too large, a necessarystrength cannot be ensured, and therefore, this point must be paidattention to. Further, although the material of the perforated panel inthis structure is an FRP, it is not particularly limited, and althoughit may be made of either an FRP or a metal, making from an FRP ispreferred from the viewpoint of durability, corrosion resistance andlightness.

The sound-proof wall having two typical structures as described aboveexhibits the following effects.

According to a first effect, since the sound insulation panel isconstructed from FRP skin members and a core, the specific strength ishigh as compared with that of a concrete or a usual metal such as aniron, providing a necessary strength as a sound-proof wall and greatlightening can be both realized, and since the shape can be designed asa shape simple and good in handling property, installation to ahigh-level place can be easily carried out without using an exclusiveconstruction apparatus such as a heavy machine. Further, in a case wherethe sound-proof wall is applied to a high-level place of a railway or aroad, because the construction body set at the high-level place can begreatly lightened, the earthquake-proof property of the high-levelbridge can be improved similarly to reinforcement of support poles ofthe high-level bridge. Further, since the FRP can be increased inresistance against moisture and chemicals by appropriately selecting thematerial of its plastic as compared with a metal such as an iron and analuminum alloy, a maintenance such as painting for preventing rust isnot necessary. However, because against ultraviolet rays the plasticgradually deteriorates and it causes the properties such as strength togradually decrease, in a case where the condition of use in outside fora long term is employed, it is possible to prevent ultraviolet rays fromentering into the interior of the structural body by providing a coloredgel coated layer or painting, as aforementioned. Further, because ofFRP, there is an advantage that a rough surface can be formed on itssurface at the same time as molding, thereby not only avoiding a dazzleaccompanying with reflected rays but also easily realizing a surfacehaving an extremely high-grade design, which has not been realized inthe conventional concrete or metal products, by utilizing a freedom ofFRP molding for forming a complicated shape, and obtaining a desirableresult in appearance.

According to a second effect, in a case where there is a restriction inattachment space, in a case where there is a restriction in weight ofthe whole sound-proof wall ascribed to the strength of a constructionbody, in a case where there is no side way for a high-level bridge andtaking measures to the noise is further required because housing isclose thereto, or in a case where reduction of great noises due torunning of high-speed cars is required, by providing a sound absorbingbody on both surfaces or one surface of the sound insulation panel, itbecomes possible to increase the sound-proof effect by absorbing anddamping the sound energy and reducing the level of the sound pressure bya vibration system due to a spring of an air layer in the porousmaterial of the sound absorbing body against the incident sound and byfurther reducing the sound energy by a vibration system based on masslaw in the sound insulation panel portion provided as an outer layer.

FIG. 16 shows a sound-proof wall.

In the structure shown in FIG. 16, a folded portion (113) extendingtoward a direction of a noise source (in this case, toward the inside)is provided on the top of a sound insulation portion (111) provided withsupport poles (112) having attachment portions to a construction body atthe lower portion of the sound insulation portion, and the foldedportion (113) is formed integrally with the sound insulation portion(111). Such a shape having a folded portion extended toward the insideexhibits an effect for reducing the sound propagating toward the frontside by diffracting the sound by the folded portion (113), andtherefore, the sound-proof effect can be further improved.

FIG. 17 shows structure in which a plurality of sound-proof walls areconnected.

In the structure shown in FIG. 17, an overlapping portion (122) isprovided on a side end portion of each sound insulation panel (121) sothat sound insulation panels (121) adjacent to each other are partiallyoverlapped. Support poles (124) each having an attachment portion toconstruction body (123) are provided on each of a plurality of soundinsulation panels (121) connected to each other, and each support pole(124) is fixed to the construction body (123), for example, via chemicalanchors (125) and nuts (126). Overlapping portion (122) is formed in astepped structure having a thickness of half of the thickness of soundinsulation panels (121), and a joint portion of sound insulation panels(121) adjacent to each other is formed by overlapping the overlappingportions (122) with each other. A structure may be employed wherein aslight gap is formed between overlapping portions (122) overlapped witheach other, and for example, a sealing material such as a sponge and thelike or a packing material such as a sealant or another material isdisposed between the overlapping portions to improve the sealability. Bysuch a structure, it is possible to improve the appearance of a seriesof sound-proof walls connected to each other and further increase thesound-proof effect. Although a structure of overlapping portions (122)overlapped with each other is employed in this embodiment, a formationmay be employed wherein fitting portions comprising recessed portions orprojected portions are provided on the respective end portions ofadjacent sound insulation panels. Further, if support poles forattachment (for example, support poles made of an H-section steel) existat a relatively small interval, the above-described overlapping portionsmay be omitted. In this case, it is possible to give a function forconnection to each other to the flange portion of each H-section steel.

FIG. 18 shows a sound-proof wall.

The sound-proof wall shown in FIG. 18 comprises a sound insulation panel(131) comprising a core (133) and FRP skin members (132) positioned onboth sides of the core, and a sound insulation body (135) comprising alight transmitting material (134). A polycarbonate, a reinforced glass,an acrylic, etc. can be used as light transmitting material (134), andamong these materials, polycarbonate having a great elongation andcapable of being thinned is preferred. The thickness of a plate ofpolycarbonate is preferably not less than 5 mm from the viewpoint ofsound-proof property, and a weather-proof sheet may be bonded to theplate in order to improve the weather-proof property. Sound insulationbody (135) is held by, for example, a metal frame (136) made of analuminum, etc., and an L-shaped attachment portion (137) is formed atthe lower portion of sound insulation panel (131). Further, supportpoles (138) extend over sound insulation panel (131) and soundinsulation body (135) to support these portions, and the support poles(138) are formed integrally with the sound insulation panel (131).However, the support poles (138) may be mechanically bonded withoutintegrally forming. Further, support poles (138) also are provided inthe L-shaped folded portion at the lower portion of sound insulationpanel (131) integrally with the portion, and they form a part ofattachment portion (137). In the sound-proof wall having such astructure, by providing a daylighting portion comprising lighttransmitting material (134), the sound-proof wall can be heightened, thesound insulation property can be improved, and limitation of sunshine toresidents in housing and buildings can be avoided without damagingvisibility for passengers. The daylighting portion is preferably formedin a structure for providing an opening portion in the sound insulationpanel and fitting the above-described light transmitting material intothe opening portion because the number of parts can be reduced.

The sound-proof wall is not limited to the structures explained above,and it is preferred that the structure is appropriately selected orcombined in consideration of an optimum formation, an attachment method,a design of the surface, etc. depending upon the attachment place, therequired attachment method, the sight nearby, the level of noise, etc.

Next, the method for producing a sound-proof wall will be explained.

As the method for producing a sound-proof wall panel; any usual methodfor molding an FRP such as hand-lay-up method and autoclave method canbe employed. Further, the panel can also be formed by cutting membersmolded by a continuous molding method such as pultrusion method atrespective required dimensions, and thereafter bonding and assemblingthem. However, it is preferred to employ a molding method such asso-called RTM or RIM method in which an integral molding is easilycarried out and lightening can be easily achieved by increasing thefiber volume content, or an integral molding method (SCRIMP method) inwhich a portion to be molded is reduced in pressure and at the same timea distribution material for a resin to be injected is disposed. Forexample, a method is preferably employed, wherein reinforcing fiberssuch as a glass fiber woven fabric and a unidirectional woven fabric ofcarbon fibers are stacked, a hard polyurethane foamed material having aspecific gravity of 0.03 to 0.1 or a wooden material having a specificgravity of 0.1 to 1.0 (for example, a balsa material or a furcatamaterial) is placed in a cavity of a mold, the inside of the cavity isvacuumed and a matrix resin such as a flame-proof unsaturated polyesterresin is injected and cured.

According to such a molding method, there is an advantage that the fibervolume content can be increased and a molded body having high strengthand stiffness can be produced relatively inexpensively. Moreover, it ispreferable because it is possible to form the metal or FRP support polessimultaneously with molding of a sound insulation panel as in thepresent invention.

We found that, to obtain the same level of sound insulation property asthat in a conventional concrete sound-proof wall at a constant thicknessof a skin member, a thickness of 50 mm or more is required in a case ofa core made of a foamed material, a thickness of 35 mm or more isrequired in a case of a wooden core, and it is possible to give strengthand stiffness capable of resisting against a wind pressure of 300 kg/m²to 400 kg/² per unit area even in the case of a core made of a foamedmaterial. Further, in the case of a wooden core, it has been found that,particularly because the shear stiffness is high, when the flexuralstrength of the whole panel is determined, a strength of about threetimes that of a foamed-material core can be obtained, and it is suitablefor a case where a higher load is applied to a panel.

Further, in the above-described molding method, it is easy to integrallyform reinforcing ribs. For example, it may be carried out thatreinforcing fibers for forming reinforcing ribs are wound around a corein advance, and a resin is impregnated into the wound reinforcing fiberssimultaneously with molding of skin members. In such a method, there isan advantage that a stable strength at a boundary between layers higherthan that in a case of bonding by adhesion can be obtained. As themethod for obtaining a sound insulation panel, except theabove-described methods, for example, a method may be employed whereinan SMC substrate is used, after separated two portions of a frontportion and a rear portion of a sound insulation panel are molded, thefront portion and the rear portion are bonded by an adhesive or bymachine bonding to form a hollow panel with a hollow portion therein,and a predetermined core material is charged into the hollow portion,and for example, an inner pressure is applied to a hollow blow-moldedbody or a balloon to form therein a portion to be formed as a core, anda predetermined core material may be charged into the inside of themolded hollow skin member.

Further, a colored layer provided as an outermost layer for mainlyimproving the appearance (improving the design) and further having afunction for preventing deterioration of a resin due to ultraviolet rayscan be formed, for example, by blowing a gel coating material or apigment-containing resin having two or more colors by an air gun, etc.Because the gel coated layer is formed by blowing a gel coating materialonto a mold in advance and forming the layer together with molding skinmembers, the gel coated layer is substantially integrated and theadhesive property is excellent. At this juncture, by disposing a matsubstrate of 200 to 450 g/m² (for example, chopped strand mat comprisingglass fibers) between the reinforcing fiber layer of a skin membercomprising a unidirectional substrate or a woven fabric substrate andthe gel coated layer, the adhesive property with the skin member can befurther increased.

On the other hand, although a surface having an irregularity of 0.5 mmor less can be formed even by blowing a high-viscositypigment-containing resin having a viscosity of 5 to 25 dPa·s to thesurface of a skin member, a sufficient decreasing is required, andbecause there may be a case where the adhesive property becomes smallerthan that in the case of a gel coated layer, it must be carried out withcare.

Further, the colored layer accompanying with a mat substrate also can bepreformed, and after a sound insulation panel is molded, it can beformed by bonding the preformed layer with an adhesive or at least thesame resin as the matrix resin via the mat.

Further, in the colored layer accompanying with a mat substrate, becausethe layer of the mat substrate does not require a strength and it is alayer for forming a rough surface, in a case where a design surface withan irregular surface of 0.5 mm or more is formed, as described above, alayer functioning to give strength and stiffness and a layer functioningto give a design can be separated into the respective different layers,and therefore, it can be prevented to cause the orientation ofreinforcing fibers for obtaining the strength and stiffness to locallybend by the influence due to the irregularity of the surface, andreduction in strength of the panel can be prevented. As the method forforming the irregular surface, although either a method for placing anelastic material such as a rubber in a mold and transferring the patternof the material, or a method for using a mold in which an irregularpattern is formed in advance on the molding surface of the mold, may beemployed, the method using the elastic material is preferred becausevarious patterns can be formed only by exchanging the elastic material.As the method for forming a design surface, for example, a method alsocan be employed wherein a thermoplastic resin sheet printed in advanceis bonded to the surface of a skin member.

Next, the FRP sound-proof wall, having a structure in which a soundabsorbing body is provided on each of or one of the surfaces of an FRPsound insulation panel and a perforated panel covering the soundabsorbing body is provided, can be obtained by forming the soundinsulation panel in advance as described above, and for example,mechanically bonding a glass wool, formed as a porous material andhaving a predetermined thickness, to the sound insulation panel with theFRP perforated panel by using vises, etc. Although the above-describedperforated panel can be obtained by perforating a plate material, whichis prepared by stacking mat substrates comprising glass fibers and wovenfabric substrates alternately while impregnating a resin and curing theresin, by machining, it also can be obtained by molding while arrangingunidirectional fibers along a lattice-type mold, and other methods maybe employed to form a target perforated panel.

EXAMPLES

Hereinafter, our walls will be explained based on examples.

Example 1

Woven fabrics of glass fibers with an orientation of 0/90° andunidirectional woven fabrics of carbon fibers were stacked asreinforcing fibers of FRP skin members, multiaxial woven fabrics ofglass fibers with an orientation of 0/±45° were disposed for formingreinforcing ribs, and by using a 30 times foamed hard polyurethanefoamed body as a core and by impregnating and curing a flame-proofunsaturated polyester resin added with 20 parts of a boromic-grouphalogenated organic substance (DBDPO) by a vacuum injection andimpregnation molding method, an FRP sound-proof wall body as shown inFIG. 8 and having a height of 1525 mm, a width of 990 mm and a totalthickness of the sound-proof portion of 56 mm was obtained. At thisjuncture, the total weight of the structural body (the same body as thatof panel 2 of Example 4 described later) was 20.6 kg, and the weight perunit area was 13.6 kg/mm².

When this molded body was attached to a base frame so that the soundinsulation panel (71) was placed horizontally, and a compression loadwas applied to the sound insulation panel (71) from the upper side inthe vertical direction by a large-sized universal tester, the rootportion of the attachment portion (72) molded integrally with the soundinsulation panel (71) was broken at a load of 20 kN. When this value ofthe load was divided by the area of the sound-proof portion of the soundinsulation panel, the divided value was about 13 kN/m², and it wasunderstood that a sufficient strength against a load applied by wind wasgiven. When a 200 mm square sample was cut out from the molded body ofthe sound insulation panel (71) and the sound insulation propertyagainst a white noise was determined, the transmission loss was 13 dB.As the result that a similar determination was carried out as to aconcrete block having a total thickness of 100 mm, the transmission losswas 22 dB.

Example 2

Employing similar substrate formation and resin, and using a pipe madeof SUS 304 (stainless) having a thickness of 2 mm and a rectangularsection of 100 mm×50 mm as the support pole having an attachmentportion, the pole was extended up to the top of the sound insulationportion and was molded integrally. At this juncture, the fiber directionof carbon fiber 0 degree woven fabric was oriented at 90° relative tothe extending direction of the SUS 304 pipe, and in the same directionas the fiber direction, ribs were disposed at four positions at a pitchof 320 mm. Further, overlapping portions as shown in FIG. 17 were formedon both ends. Thus, an FRP sound-proof wall, having a height of thesound insulation panel of 1600 mm and a total width includingoverlapping portions at both ends of 1040 mm, was obtained. The supportpole for attachment was formed in a form shown in FIG. 6 so as toproject from the lower end of the sound insulation portion by 400 mm.The total weight of the FRP sound-proof wall obtained was 42 kg, and theweight per unit area of the sound-proof portion was 25.2 kg/m².

This molded body was attached to a concrete construction body so thatthe sound insulation panel was placed horizontally, and a compressionload was applied to the sound insulation panel from the upper side inthe vertical direction by a large-sized universal. When the load wasapplied up to 5 kN and thereafter the load was removed, no change wasappeared in the structural body. Further, when the load was applied upto 7 kN and thereafter the load was removed, a slight plasticdeformation was recognized in the SUS 304 pipe forming the attachmentportion. However, because the value of the 7 kN load was divided withthe area of the sound-proof portion and the resulted value was about 4.4kN/m² it was understood that a sufficient strength against a loadapplied by wind was given. With respect to the transmission loss,because the structure of the sound insulation panel was almost the sameas that in Example 1, it was a same-level property.

Example 3

A glass wool material having a thickness of 13 mm was placed as a soundabsorbing body on the back surface of a sound insulation panel havingthe same substrate structure as that described above, and fromthereabove, an FRP molded plate having a thickness of 2 mm andrectangular openings each having a size of 95 mm×22.5 mm with a openingrate of 85% was attached to the sound insulation panel body with tappingvises via a spacer having a height of 13 mm. When the transmission losswas determined in the same condition as that described above, animprovement of the sound insulation property by 5 dB could be achieved.The total weight of this panel was 53 kg, and the weight per unit areawas 32 kg/m².

Example 4

Although only the weight and the sound insulation property wereinvestigated in Examples 1 to 3, in order to investigate relationshipsbetween the flexural stiffness, the deflection and the strength of asound insulation panel according to the present invention and thethickness of the panel, panels and single plates having structures shownin FIG. 19 were formed using the substrates shown in Table 1 at the sameconditions as those in Example 1 other than the conditions of thethickness of a skin member, the kind of a core, presence of a core andthe thickness of the core. Then, the strengths and the amounts ofdeformation of these samples were determined by carrying out afour-point bending test (load application speed: 5 mm/min.) at acondition where each sample was set at a support span of 40 times thetotal thickness of the panel or the single plate and the span wasdivided into three equal parts. Further, when the result of the bendingtest was investigated, the thickness ratio β, the proof stress ratio ηand the deformation degree Δ were defined as follows, respectively, andthe result of the test was shown in Table 2.Thickness ratio β=total thickness T/(2×thickness of skin member t1)Proof stress ratio η=bending moment at the time of breakage(kg·m)/bending moment at the time of a wind load of 300 kg/m²(2940 N/m²)Deformation degree Δ=deflection δ (mm) at a load applied condition of awind load of 300 kg/m²(2940 N/m²)/support span L (mm) at the time of thetest

The weight is related to the transmission loss, the proof stress ratiois related to the strength (=the safety factor), the flexural stiffnessand the deformation degree are related to the deflection as a structuralbody, and especially if the deformation degree is great, the panelitself is fluttered and the panel itself becomes a noise source.

FIG. 20 shows the transmission loss (dB) determined by the calculationbased on mass law. FIGS. 21, 22, 23 and 24 show the result of Table 2indicating the thickness ratio at the abscissa and the proof stress, theunit weight, the deformation degree and the flexural stiffness per unitwidth at the respective axes of ordinates. Based on these results, itwas determined whether the respective design targets necessary for asound insulation panel were satisfied. The result of the determinationis shown in Table 3. The conditions of the flexural stiffnesses per unitwidth are within the range of (0.1 to 10)×10⁷ kg*mm, and the conditionsof the thickness ratios are within a ratio T:t1 of the total thicknessof said panel T to a thickness of each skin member made of FRP t1 iswithin the range of 5:1 to 50:1.

The following matters are understood from the results exhibited in theseTables and Figures.

(A) The transmission loss can clear the target value over the entirerange of frequency in panel 1, panel 2 (the same structure as that inExample 1), panel 3, panel 4 and single plate 1 of Example 4 as long asthe unit weight is 10 kg/m² or more.

(B) As to the strength (=proof stress) and the stiffness which aremechanical properties, although panel 1, panel 2, panel 3 and panel 4 ofExample 4 satisfy the target values of all the proof stress η, theflexural stiffness per unit width EI and the deformation degree Δ, thesingle plates do not satisfy the target values even if the weights arealmost the same. From this, as aforementioned, it is clarified that thesandwich structure is a structure suitable for a sound insulation panel.From the deformation degree, it is understood that the deformation canbe suppressed small if the flexural stiffness per unit width is withinthe range of (0.1 to 10)×10⁷(kg·mm). However, although panel 3 is alight sandwich panel, the proof stress (=safety factor) is 1.1, if aload of 400 kg/m² (3920 N/m²) greater than 300 kg/m² (2940 N/m²) issupposed as the wind load, the strength becomes insufficient. From this,it is understood that the thickness ratio β, which is determined bydividing the total thickness T with the sum of the thicknesses t1 ofskin members facing each other, is necessary to be 5:1 or more.

TABLE 1 Structure Used substrate A Glass chopped strand mat (Weight: 230kg/m²) B Unidirectional woven fabric of carbon fibers (Weight: 300kg/m²), Longitudinal direction B′ Unidirectional woven fabric of carbonfibers (Weight: 200 kg/m²), Longitudinal direction C Glass fiber 0/90°woven fabric (Weight: 1890 kg/m²) C′ Glass fiber 0/90° woven fabric(Weight: 1260 kg/m²) CRU 30 times foamed hard polyurethane foamedmaterial, t = 180, 50, 15 mm CRB Balsa core with a specific gravity of0.1, t = 38 mm

TABLE 2 Thickness ratio Unit weight Proof stress Flexural stiffness perunit Deformation Sample β Wt(kg/m²) ratio η width EI × 10⁷(kg · mm)degree Δ panel 1 31.0 15.8 10.6 10.0 2890 panel 2 9.3 13.6 10.3 0.9 231panel 3 3.5 10.8 1.1 0.1 206 panel 4 7.4 14.6 10.7 0.8 227 Single plate1 1.0 10.2 0.4 0.005 62 Single plate 2 1.0 6.8 0.2 0.001 37 Target ofdesign 5/1~50/1 Transmission loss: 1 or more 01.~10 200 or more targetvalue or more

TABLE 3 Thickness Property of Proof stress Flexural stiffnessDeformation Synthetic Sample ratio transmission loss ratio per unitwidth degree judgment panel 1 31.0 ◯ (15.8) ◯ ◯ ◯ ◯ panel 2 9.3 ◯ (13.6)◯ ◯ ◯ ◯ panel 3 3.5 ◯ (10.2) ◯ ◯ ◯ ◯ panel 4 7.4 ◯ (14.6) ◯ ◯ ◯ ◯ Singleplate 1 1.0 ◯ (10.2) X X X X Single plate 2 1.0 X (6.8) X X X X Targetof design 5/1~50/1 Target value or more 1 or more 01.~10 200 or more ◯:acceptable as design specification/ X: unacceptable as designspecification ( ) Value in parenthesis: weight per unit area kg/m²

Comparative Example 1

The weight per unit area of a light concrete block of type A having atotal thickness of 100 mm, which has almost the same sound-proofproperty, is 100 kg/m². With respect to such a light concrete, the noiselevel of an existing conventional concrete block sound-proof wall, whichwas constructed by stacking concrete blocks each having a width of 390mm, a height of 190 mm and a thickness of 10 mm by eight in the verticaldirection (total height: 1520 mm) and connecting a number of the blocksto each other in the width direction, at the time of train passing, wasmeasured at a place distant from the sound-proof wall by 6 m using anoise meter. As a result, the noise level was 71 dB. While the height ofthe sound-proof wall was kept as it was 1520 mm, the sound-proof wallwas cut and removed successively by each width of 800 mm. At that time,when the weight of each removed portion was measured, it was 134 kg, andthe weight per unit area was 110 kg/m².

After that, the FRP sound-proof wall shown in Example 1, which had atotal weight of 20.6 kg, a weight per unit area of 13.6 kg/m², a heightof 1525 mm, a width of 990 mm and a total thickness of the sound-proofportion of 56 mm, was installed over 24 m, and the noise level at thetime of train passing was measured at the same condition as thatdescribed above. As a result, the noise level was 70 dB, and theachievement of the same-level property was proved.

Comparative Example 2

The existing sound-proof had been constructed such that panels eachhaving a width of 1980 mm, a height of 600 mm and a thickness of 60 mmhad been stacked by three (total height: 1800 mm) between metal supportpoles provided at an interval of 2000 mm, a number of the panels hadbeen connected to each other in the width direction, and cement platesmade by extrusion (weight per unit area: 70 kg/m²) had been used for thesound insulation panel portion of the sound-proof wall. Exchange of thewall was decided from the reason of the existence of cracks, etc., andwhen the noise level at the time of train passing was measured beforethe exchange, the noise level was 75 dB. After the removal of theexisting wall, the flat-type FRP sound-proof panels, each of which has astructure shown in Example 2 in that metal pipes were inserted at bothend portions in the width direction, were produced and installed (weightper unit area: 24.2 kg/m², each panel having a width of 1980 mm, aheight of 900 mm and a total thickness of the sound-proof portion of 56mm). Then, as the result of measuring the noise level at the time oftrain passing similarly, the noise level was 72 dB. Before and after theexchange, almost the same sound insulation property could be obtained.

Comparative Example 3

The single plate 2 prepared in Example 4 had a unit weight of 6.8 kg/m²,and as is evident from the graph of the transmission loss shown in FIG.20, it is clear that the single plate did not satisfy the target soundinsulation property. Where, even in the same single plate structure, itis understood that the single plate having a unit weight of 10 kg/m² ormore can satisfy the sound insulation property.

INDUSTRIAL APPLICATIONS

In the FRP sound-proof wall panel, the FRP sound-proof wall using thispanel and the method for producing the same, since the sound insulationportion, which is the main structural portion thereof, is made of FRPhaving a strength and a ductility, it does not cause propagation ofcracks due to repeated application of a small force, which is aphenomenon peculiar in a brittle material such as a conventionalconcrete sound-proof wall, and ultimately, occurrence of flaking anddropping of small pieces due to corrosion can be prevented. Therefore,an optimum sound-proof wall having no fear of flaking and deteriorationcan be provided for use in railways and roads.

Further, as compared with a concrete or a general metal such as an iron,the specific strength is high, and a great lightening can be expectedwhile a strength necessary for a sound-proof wall is kept, and as aresult, in an installation place such as a high-level bridge, theinstallation to the high-level place can be facilitated by makingconveying of a heavy machine for lifting unnecessary, etc.

Furthermore, by providing an attachment portion to a construction bodyto the lower portion of the structural body, the structural body itselfcan be solely installed to the construction body, and as compared with ageneral-structured sound-proof wall requiring poles or bridesseparatedly, the steps and the time for installation can be suppressedsmall. Further, by providing a sound absorbing body on each or one ofthe surfaces of a sound insulation panel and forming an at leastthree-layer structure including a perforated panel which covers thesound absorbing body, the sound-proof effect can be further increased byusing together the sound-proof wall comprising the sound insulationpanel and the sound absorbing body, particularly in a case where thesound insulation property as the sound-proof wall is required at ahigher level, such as a case where there is only a little space forinstallation, a case where apartments and housing are present moreclosely, a case where the weight as the sound-proof wall is restricted,etc.

1. A sound-proof wall panel made of FRP comprising a core and skinmembers made of FRP positioned on both sides of said core, and havingweight per unit area of 10-60 kg/m2, wherein at least one surface ofsaid panel is formed as a rough surface in which convex parts andconcave parts are disposed at random and a mean value of differences inheight between said convex parts and said concave parts is 0.5 mm ormore, and said rough surface is formed as a light irregular-reflectionsurface.
 2. A sound-proof wall panel made of FRP comprising a core andskin members made of FRP positioned on both sides of said core, andhaving weight per unit area of 10-60 kg/m², wherein said panel has astructure with at least three layers of a sound insulation panelportion, a sound absorbing body and an FRP perforated panel portion, anda folded portion extending toward an inside portion of said panel isprovided on a top of said panel, and said folded portion is moldedintegrally with said sound insulation panel portion.
 3. The sound-proofwall according to claim 1, and a support pole which supports said paneland has an attachment portion attached to a construction at a lowerposition, wherein an overlapping portion is provided on a side endportion of each panel so that panels adjacent to each other partiallyoverlap, and a packing material is filled between overlapping portionsof said panels adjacent to each other.
 4. The sound-proof wall accordingto claim 1, and a support pole which supports said panel and has anattachment portion attached to a construction at a lower position,wherein a stiffener is fixed to an outside portion of said panel or saidsupport pole.
 5. The sound-proof wall according to any of claims 1 to 2,wherein a matrix resin of said skin members made of FRP comprises athermosetting resin containing both of a flame retardant and a dampingagent or one of them.
 6. The sound-proof wall panel according to any ofclaims 1 to 2, wherein reinforcing fibers of said skin members made ofFRP comprise at least one selected from the group of glass fibers,carbon fibers and aramide fibers.
 7. The sound-proof wall panelaccording to any of claims 1 to 3, wherein volume content of reinforcingfibers in said skin members is 15-60%.
 8. The sound-proof wall panelaccording to any of claims 1 to 2, wherein flexural stiffness per unitarea of said sound-proof wall panel is (0.1 to 10)×10⁷ kg*mm.
 9. Thesound-proof wall panel according to any of claims 1 to 2, wherein 5-20%of the total thickness of a portion made of FRP comprises an FRP layercontaining carbon fibers as reinforcing fibers.
 10. The sound-proof wallpanel according to any of claims 1 to 2, wherein the ration T:t1 oftotal thickness of said panel T to a thickness of each skin member madeof FRP t1 is 5:1 to 50:1.
 11. The sound-proof wall panel according toany of claims 1 to 2, wherein reinforcing ribs are provided at aninterval of 10-500 mm in the vertical and horizontal directions or oneof the directions for integrally joining said skin members made of FRPfacing each other.
 12. The sound-proof wall panel according to any ofclaims 1 to 2, wherein a vertical section of said panel is formed as awave shape, a hat shape or an arc shape.
 13. The sound-proof wall panelaccording to claim 1, wherein an FRP skin member forming said roughsurface has at least two layers of a layer forming said rough surfaceand a lawyer for obtaining a strength and a stiffness of said panel. 14.The sound-proof wall panel according to claim 1, wherein an FRP skinmember forming said rough surface has a colored layer as an outermostlayer.
 15. The sound-proof wall panel according to claim 1, wherein saidrough surface is covered with a color gel coated layer as a brick layingpattern.
 16. The sound-proof wall panel according to any of claims 1 to2, wherein said panel comprises a perforated panel having an openingrate of 50-90%.
 17. The sound-proof wall panel according to claim 2,wherein said sound insulation panel portion comprises a sandwichstructural body containing a core between FRP skin member facing eachother.
 18. The sound-proof wall panel according to claim 2, wherein saidsound insulation panel portion comprises a stiffener structural bodyhaving an FRP reinforcing material on one surface of an FRP singleplate, said FRP reinforcing material substantially being integrated withsaid FRP single plate in its lengthwise and crosswise directions oreither direction.
 19. The sound-proof wall panel according to claim 2,wherein said sound absorbing body comprises a porous material.
 20. Thesound-proof wall panel according to claim 2, wherein said soundinsulation panel portion comprises a sound insulation panel for an FRPsound-proof portion which is formed from said skin members made of FRPand said core, and a sound insulation panel for a sound-proof portionwhich is formed from a light transmitting material.
 21. The sound-proofwall panel according to claim 20, wherein said light transmittingmaterial is made of a polycarbonate, a tempered glass or an acrylic. 22.The sound-proof wall panel according to any of claims 1 to 2, whereinsaid core is made of a foamed material or a wooden material.
 23. Thesound-proof wall according to any of claims 3 to 4, wherein panels areconnected to each other and integrated via a support pole disposedbetween said panels.